In disc brakes, it is common for a caliper to straddle a rotor that is fixed to an axle of a vehicle with the caliper being located on a stationary member that is secured to the housing of the vehicle. The caliper has a housing with a bore therein which holds an actuation piston and a square seal is located in a groove in the housing that engages the piston to seal the bore and define an actuation chamber. A first friction member is connected to the actuation piston and a second friction member is connected to an arm extending from the caliper. The first and second friction members are located on opposite sides of the rotor and when pressurized fluid is supplied to the actuation chamber, the piston and caliper move in such a manner that the first and second friction members engage the rotor to effect a brake application. The following U.S. patents are illustrative of disc brake and their corresponding functional operation: U.S. Pat. Nos. 3,113,643; 3,421,604; 4,530,423; 4,809,821; 5,713,435; and 5,826,681. All of the disc brakes disclosed by these patents while possessing different structural components operate in a similar manner to effect a brake application in a manner as describe above and in returning the piston to a position of rest through a square seal. The square seal functions in an adequate manner, however, the square seal is in direct contact with the pressurizing fluid, maybe effected by extreme changes in temperature and may lose some internal resiliency after a period of time and as result may change or alter the time required to return the piston to a position of rest.